Process of producing pulverulent and easily-washable hydrates of aluminium.



N. A. LANGLET & E. L. RINMAN. PROCESS OF PEODUGING PULVERULENT AND EASILY WASHABLE HYDRATE OP ALUMINIUM.

APPLICATION FILED MAY 29, 1908.

Patented Ja11.23, 1912.

, of the precipitated substance,

zation or by disturbed Uur-rui) sTA'rEs PATENT on ion.

SWEDEN.

NiLs ABRAHAM LANGLET, or Go'rTnNBo-RG, AND Enix LUnvIG RINMAN, or UPPsALA.

PROCESS OF PRODUCING- PULVERLENT AND EASILYWASHABLE, HYDRATES 0F y Y ALUMINIUM.

i,oi5,4.99.

Specication of Letters Patent.

Application filed May 29, 1908. Serial No. 435,652.

To all whom it may concern:

Be it known that we, NiLs ABRAHAM LANGLET, a subject of the King of' Sweden, and resident of Gottenborg, in the Kingdom of Sweden, and ERIK LUDviG Rini/IAN, a sub# ject of the King ofv Sweden, and resident of Uppsala, in the Kingdom of-Sweden, have invented new and useful Improvements in Processes of Producing Pulverulent and Easily-Washable Hydrate of Aluminium, of which the following is a specification, reference being,l had-to the drawing accompanying andv forming a part hereof.

It is' well known that the hydrate of aluminium obtained if a water solution of an aluminium salt is treated with an alkali, for instance if a solution of aluminium sulfate is treated with ammonia, is colloidal and practically impossible to filter and wash.

The object of the invention is to make it possible to obtain a pulverulent precipitate which may be easily filtered and easily washed. j

The invention consists, chiefly, in introducing the aluminium salt from which the precipitate is to be obtained, in a finely divided state, into .thepprecipitating alkali. By proceeding in sucli manner, each of the small particles of the aluminium salt is immediately covered by a thin film or pellicle by whiclithe aluminium salt is prevented from diffusing into the solution. On account thereof, hy-

drate of aluminium is obtained as a precipitate consisting of small grains of about the same size as that of the particles of thel alu minium salt introduced into the precipitant.

The aluminium salt maybe supplied to the precipitanteither in a in the form of a solution. In the former case,I the aluminiumsalt is supplied in the form of a fine powderobtained by pulvericrystallization, the latter being preferable, since in such case a more homogenous powder is generally ob tained. If, on the other hand, the valuminium salt is supplied in the form-of Va solution, said solution is. preferably sprinkled or sprayed by an atoinizer, such as a Krtings or a centrifugal sprayer, into the precipitant. The'precip'itant may be'a gas, for instance ammonia, or a liquid, such 'as ammonia wat-er, or both a gas and a l1quid.

If, the precipitant lis a gas, the precipitate water. y preferably driven out by heating the prc` 'y solid state ory obtained `should `first be washed with a water solution of the precipitant, in order that the washing shall be as effective as pos- Patented Jaaaaioia'.

sible. It has, however, been found incon'# Avement to treat an aluminium salt with a gas, for instance ammonia, solely, since in practice this cannot be made without the so-- lution becoming heated, which prevents 'a complete removal of the mother-liquor by washing on account of the mother-liquor being incased due to the hydrate of aluminium being transformed by heating into a more insoluble form. A better result is obtained if an alkaline liquid -is used as a precipitant,

,or if a supercialprecipi-tation is effected 'by a gas and theprecipitation is thereupon completed by a precipitant in solution. The latter is generally the case if the aluminium salt is introduced into ammoniawater, in which case the finely divided aluminium salt has to 'pass a more or less ammonical atmosphere before it reaches the solution.

By lthis means each particle of the aluminiumsalt is coated by a thin layer of hydrate of aluminium without the precipitation being suiicient to cause any considerable heating. The precipitation is thoreupon completed in the ammonia water withoutany heating taking place. O'n account thereof the precipitate obtained maybe easily freed from all ltraces of ammonium salts vby washing with dilute ammoniav The last remains of ammonia are cipitate.

In orde that our invention may be more easily understood, we will now describe two examples of carrying the process into elicot,

reference Abeing had to the drawing, in'

which- Figure 1 is a of apparatus for vintroducing a solution of an aluminium salt, such as aluminium sulintoa liquid precipitant. Fig. 2 shows fate,

diagram showing a system.

the wellknown spreader called' lKrtings sprayer. Fig. 4t", shows a device for introducing an aluminium salt, in a powdered state, such as powdered alum, into the precipitant. l' l Referring first to Fig. 1, the solution of aluminium sulfate is held in a receptacle a under pressure supplied through a pipe o r tube b suitably provided with a cock c. They solution is withdrawn through a tube d prolios ' tion of the contents of the said receptacle is vided with a cock Thespreader h is sei cured to the end of the tube d, suitably by I rior of the cone and having a spiral groove Z through which the liquid under pressure is pressed in order to lthereby obtainy arapidly rotating movement and be sprayed, by the centrifugal force, when issuing through the hole m at the apex'o'fthe cone. The rain or spray orl liquid thus obtainedv drops into a receptacle n (Fig. 1) containing the liquid preclpitant (ammonia water). The agitaveffected by a stirring device o driven by beltingvp or otherwise. The precipitate obtained is separated by filtration, preferably with the aid lof vacuum (so-called nutschfiltration), and ycontinuously washed with diluteainmonia fwater at usual temperature. After washing, the remaining water. is pressed away and ,the ammonia is driven off by heating. Ifthe precipitant is agas or a combination of a gas and a liquid, it may be necessary to replace the receptacle n by an air tight chamber. This is especially-necessary if the precipitant consists of a light gas.

- As a second example, pulverulent and easily washable hydrate of aluminium may be produced from an ammonium-alum-powder by precipitation withv ammonia. The alum-powder, preferably obtained by'disturbed crystalhzatiom'is heldy in a recepta- 4 cle g (Fig. 3), from which it is introduced by a conveyer screw .1* into va 25 per cent. water solution of ammonia. The quantity of 'alum supplied is somewhat less than `the equivalent quantity of ammonia so that the solution will always be alkaline. The pulpy mass obtained should stand for some hours with or without agitating so as to obtain a complete neutralization. The mass is thereuponl treated in the same manner as according to the first example for separating the mother-liquor from the hydrate of aluminium obtained.

We claim: v

l1. The process of producing pulverulent and easily' washable hydrate of aluminium which consists in introducing an aluminium salt in a finely divided state into a precipitating alkali, substantially as and for the purpose set forth.

2. The process of producing pulverulent and easily washable hydrate of aluminium which consists in introducing an alum-powder into ammonia water, substantially as and for the purpose set forth.

-3. The process of producing pulverulent and easily washable hydrate lof aluminium which consists in introducing an alum-powder into ammonia water of a concentration of about 25 per cent., and thereafter washing the pulverulent precipitate with dilute ammonia water at ordinary temperature.

In testimony whereof we have signed our namesto this specification in the presence of two subscribing witnesses. f

- NILs ABRAHAM LANGLET. i

,ERIK LUDVIG RINMAN.

Witnesses v AUG. SRENsEN, KARL `RUNnsKoct 

